The invention relates to shaped articles, in particular packaging material, preferably tubing, comprising a plasticized cellulose composition, water and, if appropriate, a secondary plasticizer. In particular, the invention relates to such a shaped article in the form of a tubing, which further comprises a reinforcement of fibrous material, in particular a nonwoven fleece, preferably a nonwoven fleece of long-fibered paper, incorporated in its wall.
The invention also relates to the use of tubing according to the invention as a packaging material, e.g., a packaging material adapted for food packaging, in particular as an artificial sausage casing. Artificial sausage casings of this type are not intended for human consumption.
Furthermore, the invention comprises a process for preparing the shaped articles according to the invention.
Shaped articles of cellulose hydrate, in particular packaging material, can be readily disposed of after use by burning them, and they have the further advantage that they undergo bacterial decomposition relatively rapidly.
A further advantageous characteristic of shaped articles of this type is that such a cellulose hydrate packaging material changes its properties while it is in use. This property is particularly important in the case of sausage casing, since it is necessary that the sausage casing always adapts itself to the shrinking sausage material so that the resulting sausages are always well filled and of attractive appearance.
Tubular casings of synthetic polymers, such as polyamide, polyester, polyvinylidene chloride of the like, do not show this advantageous behavior to the required degree, due to their inert properties.
For this reason, sausages with casings of the above polymers frequently become wrinkled and unattractive in an undesired manner and thus unsaleable.
The properties and the structure of the cellulose hydrate forming the shaped articles can be varied within wide limits by means of the properties and the composition of the starting viscose solution, the average degree of polymerization, the spinning conditions and drying conditions during the manufacture of the shaped articles and the plasticizer content thereof.
It has also been proposed to improve the suppleness of plasticizer-free cellulose hydrate by adding fat-like chemical substances which are capable of crosslinking. Hitherto, however, it has not been possible to completely prevent, or to even adequately limit, the very extensive changes of structure and properties which for example occur in plasticized shaped cellulose hydrate articles, when these shaped articles largely lose their content of plasticizer as a result of contact with water and/or drying.
In case of synthetic water vapor impermeable sausage casings which are made of a cellulose hydrate which has been plasticized by means of a secondary chemical plasticizer and which are coated on their inside with a polymer film, extensive shrinkage of the skin occurs after removal or loss of the secondary plasticizer. Such a removal of the secondary plasticizer from the casing material is unavoidable during the manufacture of sausages. This shrinkage leads to a high internal pressure coupled with a simultaneous embrittlement of the cellulose hydrate so that there is a risk that these skins, in most cases, will tear over the entire length of the skin when the sausages are cut open.
If the tearing of the skins is prevented by previously moistening or cooling the sausage skins, a considerable part of the sausage material is pressed out through the cut surface in an undesirable manner as a result of the high internal pressure.
Since the prior art sausage casings become embrittled due to the loss of plasticizer, sausages of this type, that is their skin, are sensitive to shocks in transit.
The above mentioned undesirable properties of sausage skins of cellulose hydrate also cannot be prevented by using skins which contain a portion of fat-like cross-linking agents.